would-be suicide bomber was actually a British national, working through British intelligence to infiltrate the terror organization in Yemen.

The spy who helped Western intelligence agencies thwart a plot to bomb a U.S.-bound airliner was a British national of Middle Eastern origin, sources tell NBC News.

The sources, speaking on condition of anonymity, also say that British intelligence was “heavily involved” in recruiting the spy, who has not yet been identified publicly, and penetrating the plot by al-Qaida in the Arabian Peninsula to detonate a new, more sophisticated underwear bomb aboard a U.S. jetliner.

A senior U.S. counterterrorism official, also speaking on condition of anonymity, would say only that multiple friendly security services were involved in the operation. Saudi Arabia’s counterterrorism operation also were involved, other U.S. officials have told NBC News.

U.S. and British officials have long reported that AQAP has wanted to recruit Muslims with Western passports to carry out attacks like the one revealed this week. As an example, the officials cited AQAP’s recruitment of Umar Farouk Abdulmutallab, who failed in the Christmas Day 2009 attempt to bring down Northwest Airlines Flight 253 over Detroit.

U.S. officials have said previously that the bomb — a refined version of an “underwear bomb” used in two previous failed terror plots — was driven out of Yemen by the insider into Saudi Arabia. It is now in the hands of U.S. bomb experts at the FBI labs in Quantico, Va., where experts have been examining it for a week, the officials said. The infiltrator also is safely out of Yemen.

The insider also provided information that allowed the U.S. to launch a Predator drone strike that killed AQAP’s operations chief, Fahd al-Quso, senior U.S. officials told NBC News on Tuesday.

Evan Kohlmann, NBC counterterrorism analyst, said he found earlier reports that the spy was a Saudi national not very credible.

“AQAP was going to give a suicide bomb to someone with a Saudi passport?” Kohlmann asked rhetorically. “AQAP has been looking for bombers with Western passports, not those who would raise suspicions.”

He noted that Abdulmutallab, who tried to detonate an earlier version of the underwear bomb aboard the Northwest flight, better fit the profile AQAP was looking at: a young upper class college student with a Nigerian passport and a multiple-entry U.S. visa. A British national would attract even less attention, he said.

Robert Windrem is a senior investigative producer for NBC News; NBC News Justice Correspondent Pete Williams and Jonathan Dienst of WNBC-TV contributed to this report.